The relative frequency density of occurrence of an event is the relative frequency of i divided by the size of the bin used to classify i.

In biology, relative frequency is the occurrence of a single gene in a specific species that makes up a gene pool.

The limiting relative frequency of an event over a long series of trials is the conceptual foundation of the frequency interpretation of probability. In this framework, it is assumed that as the length of the series increases without bound, the fraction of the experiments in which we observe the event will stabilize. This interpretation is often contrasted with Bayesian probability.